Annual report pursuant to Section 13 and 15(d)

Summarized Activity Related to Unrecognized Tax Benefits (Detail)

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Summarized Activity Related to Unrecognized Tax Benefits (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Tax
      
Reconciliation of Unrecognized Tax Benefits [Line Items]      
Beginning Balance $ 284 $ 266 $ 388
Additions for tax positions of the current year 13 16 41
Additions for tax positions of prior years 17 45 76
Reductions for tax positions of prior years for:      
Changes based on facts and circumstances (50) (27) (214)
Settlements during the period (11) (6) (23)
Lapses of applicable statute of limitations (1) (10) (2)
Ending Balance 252 284 266
Interest Expense
      
Reconciliation of Unrecognized Tax Benefits [Line Items]      
Beginning Balance 95 86 97
Additions for tax positions of prior years 6 25 27
Reductions for tax positions of prior years for:      
Changes based on facts and circumstances (9) (10) (34)
Settlements during the period (19) (3) (4)
Lapses of applicable statute of limitations   (3)  
Ending Balance 73 95 86
Penalties
      
Reconciliation of Unrecognized Tax Benefits [Line Items]      
Beginning Balance 7 8 10
Additions for tax positions of prior years   2 2
Reductions for tax positions of prior years for:      
Changes based on facts and circumstances (2) (3) (3)
Settlements during the period (1)    
Lapses of applicable statute of limitations (1)   (1)
Ending Balance $ 3 $ 7 $ 8